INTEGRATED WATER-VAPOR CONTENT BY SCANNING RADIOMETRY

Radiometry at the water vapour line with a scanning antenna beam from horizon to horizon through the zenith, in the vertical plane, was show n to be useful in estimating the integrated water vapour content from the zenith angle variation of radiometric temperature. The beam scanni ng may be made at a rate slower than the radiometer time constant usin g a Dicke type radiometer. Alternatively, a fast scanning beam may be used in a total power radiometer with a synchronous detection of the r adiometer output at the scanning frequency to obtain a space domain Di cke switching for the measurements. A simultaneous scanning beam with 22.235 and 31.4 GHz radiometers would allow us to separate the liquid water, if any, from the integrated water vapour content. Theoretical s tudies of the scanning beam radiometer performance in the estimation o f integrated water vapour content from radiosonde data is presented an d some typical results of Dicke type scanning beam radiometers at 22.2 35 and 31.4 GHz are also presented in this paper.